The common understanding of diabetes mellitus includes two types: type one and type two. But there’s a third type that’s been around for a while you may not have even heard of—and some doctors think it’s being misdiagnosed.

Type 3c diabetes, or “Diabetes of the Exocrine Pancreas,” is a third type caused by pancreatic damage. But a recent study found that doctors were likely misdiagnosing this form of diabetes as type 2. But the two require different treatment.

“Several drugs used for type 2 diabetes, such as gliclazide, may not be as effective in type 3c diabetes,” Andrew McGovern from the University of Surry wrote in The Conversation. “Misdiagnosis, therefore, can waste time and money attempting ineffective treatments while exposing the patient to high blood sugar levels.”

Scientists have recognized other types of diabetes aside from type-1 (the body destroys its own insulin-producing cells) or type-2 (the body can’t make enough insulin) for a long time. Back in 2008, researchers worried that type 3c had been under- and misdiagnosed. A new study, published recently in the journal Diabetes Care, adds further evidence to that worry after a search through millions of health records in the United Kingdom.

The researchers found over 30,000 adult-onset cases of diabetes, and found 559 occurred after pancreatic disease. Despite the link between pancreatic disease and type 3c diabetes, 88 percent of those cases were still diagnosed with the more common type of adult-onset diabetes, type 2 diabetes and only 3 percent diagnosed as type 3c—implying at least some level of misdiagnosis. Those with diabetes following their pancreatic disorder generally had worse control over their blood sugar and required more insulin.

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Obviously this is an observational study based on some assumptions, so there isn’t proof of misdiagnosis. Additionally, the implied type 3 diagnoses made up a tiny fraction of total adult onset cases, though more common than type 1. The results still concerned McGovern. “Our findings highlight the urgent need for improved recognition and diagnosis of this surprisingly common type of diabetes,” he wrote.

The lack of recognition is clear. Despite publishing the study in one of their journals, the American Diabetes Association does not mention diabetes types aside from 1, 2, and diabetes associated with pregnancy on their website. They did not return a request for comment. Diabetes UK does mention other types, though not explicitly cases following pancreatic disease. Still, “It’s essential that all people with diabetes receive the correct diagnosis, so that they have access to the right care and treatment to manage their condition effectively, and reduce their risk of complications,” said Douglas Twenefour, Diabetes UK Deputy Head of Care in a statement passed to Gizmodo.

What does this mean for you? Well, if you’re concerned you’ve been misdiagnosed, perhaps show your doctor McGovern’s article. McGovern wrote: “Correctly identifying the type of diabetes is important as it helps the selection of the correct treatment.”

Update 10/24/17 5:50PM: The American Diabetes Association passed along their Standards of Medical Care for 2017, which includes a one mention of “diseases of the exocrine pancreas” under “specific types of diabetes due to other causes.”